Wireless local area networks (WLAN) are becoming prevalent in many environments. To facilitate implementation of WLAN, the Institute of Electrical and Electronic Engineers (IEEE) has developed standards and protocols for such networks. These standards are commonly referred to as the IEEE 802.11 standards (802.11a, 802.11b, and so forth). To improve Quality of Service (QoS) for different applications working over Wireless LAN, including voice and video transmission, the 802.11e standard has been developed.
An 802.11 WLAN network is typically made up of a group of nodes forming a cell called Basic Service Set (BSS). A node may be an access point (AP) or a station (STA). When the WLAN is operating under the 802.11e standard, the access point (AP) and the station (STA) are typically referred to as QAP and QSTA. A QAP is usually physically coupled to a wired network such as a local area network (LAN). The QAP within an 802.11e WLAN cell will further be in wireless communication with one or more STAs. In such a cell, there is typically only a single wireless medium or channel (e.g., band) that can be used for communicating between the nodes.
The IEEE 802.11e standard is a protocol that defines methods to provide QoS service over WLAN for variety of applications including video- and audio-type applications. Further, the 802.11e standard is based on two primary mechanisms for channel access.
The first mechanism is the Enhanced Distributed Channel Access (EDCA) protocol, which is a contention-based mechanism employing a contention window (CW) method with random backoff to determine which node within a cell has the right to transmit signals. That is, when EDCA is employed, the various nodes of a cell will compete during a specific time period (i.e., contention window) to determine which node(s) is/are permitted to transmit signals.
The second mechanism is the Hybrid Coordination Function (HCF) Controlled Channel Access (HCCA) protocol, which originates from the legacy Point Coordination Function (PCF). The HCCA mechanism is basically a polling-based protocol whereby a QAP polls each QSTA within its cell whether or not each of the QSTAs wishes to transmit data (signals) and if so, to allocate an increment of time to transmit the data. The time period assigned to a node for transmitting data (i.e., signals) may be referred to as the “transmission opportunity” (TxOP).
Prior art nodes have resorted to complicated and/or inefficient architectures to concurrently support the two mechanisms (EDCA and HCCA).